As presented in U.S. Patent Application Publication Number 2014/0334049 (assigned to Intel Corp. of Santa Clara, Calif.), one-time programmable fuse arrays (e.g., programmable read-only memories) may store various values (fuse values) in a Central Processing Unit (CPU), System-on-a-chip (SoC), and the like. These fuse values may relate to security keys, activation of various CPU/SoC features, and functions such as cache memory size. The fuse values may be programmed using ultra high voltages (e.g., >2.2V), whereas the CPU may operate at a much lower voltage (e.g., 1.0V). In-Field-Programmable (IFP) fuse arrays are one-time programmable fuses used for storing customer specific data (i.e., fuse values). IFP fuse arrays may store specific security keys that devices (e.g., mobile computing nodes such as Smartphones) use to function on a mobile carrier's network, store data that enables or disables various functions and features of the SoC platform, and provide for encryption/decryption, authentication, and the like.
Maliciously accessing or otherwise manipulating fuse values can pose any number of problems, such as improperly unlocking various features in a chip by overriding fuse values or accessing customer security keys. One way of unlocking a processor (e.g., CPU) by disrupting fuse values is through voltage level manipulation. Voltages may be supplied from a motherboard (outside of the die and package) and are, consequently, susceptible to manipulation through physical access of voltage pins. Changing supply voltages affects how much current can flow through a primary fuse cell as well as a reference fuse cell (which is used to develop a voltage differential at sense amplifier inputs). Changing supply voltages can also affect a sensing clock that controls how long a sense amplifier is enabled. Doing so distorts the current voltage values communicated into the fuse sense amplifier. Doing so also can reduce or increase the time required to develop the sense amplifier differential, which in turn can corrupt the fuse values that are being read out depending upon the design.